Block-signal system.



L. A. HAWKINS.

BLOCK SIGNAL SYSTEM. APPLICATION FILED JULY 22, 190B. RENEWED 001211, 1910.

2 SHEETS-SHEET 1.

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Patented Apr. 28, 1914.

2 SHEETS-SHEET 2.

L. A. HAWKINS.

BLOCK SIGNAL SYSTEM. APPLICATION FILED JULY 22, 1908. RENEWED 0013.11, 1910.

17122212255175 INVENTUR WQQQM l2! UHEJY'CE' A. HAWKINS.

5 m w BY :OLuMBIA PLANOGRAPH CO.,WASHINUTON, D. c.

UNITED STATES PATENT OFFICE,

LAURENCE A. HAWKINS, OF SCHENEC'IADY, NEVJ YORK, ASSIGNOR, BY MESNE AS- SIGNMENTS, TO THE UNION Sl/VITCH AND SIGNAL COMPANY, A CORPORATION OF PENNSYLVANIA.

menses Patented Apr. 28, 1914,

Application filed July 22, 1908, Serial No. 444,744. Renewed October 11, 1910. Serial No. 586,558.

To 072 71720777, 2'25 m (13 concern:

Be it known that I, LAURENCE A. Haw- KINS, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Block- Signal Systems, of which the following is a specification.

My invention relates to block signal systems for electric railways, in which the rails are continuous for all currents, comprising sources of alternating current connected across the rails at intervals, and a pair of relays supplied with current from the tracks between each two adjacent sources, each relay responding to current from one adjacent source only. In such a system, a block or block section may extend from one source to the next, or from one pair of relays to the next, according as a pair of relays are connected to control the same or different signals. One such system, in which the block extends from one source to the next, is described in my former application, No. 329,3et7, filed August 6, 1906. In such a system a train approaching a source of current at the entrance to a block, reduces its voltage and gradually dee'nergizes the relay supplied from that source. The point at which the relay drops its contact and causes the signal to go to danger is consequently not absolutely fixed. While it can be fixed sufficiently closely for all practical purposes by employing transformers of good regulation, and using a high frequency signal current, so that the impedance of the rails to the signal current is high, it is sometimes advantageous to provide other means for fixing the point at which the signal goes to danger. This may be done either to fix the point more definitely than would otherwise be the case, or to save power, since when such means are employed the transformer need not have good regulation, and consequently the current delivered by the transformer, when a train is standing across its secondary terminals, is not high. One arrangement for definitely fixing the point at which the signal goes to danger is described in my former application, Serial No.- 37Sg2t3, filed June 10, 1907. In the system disclosed in that application I employed a short insulated rail section.

The purpose of my present invention is to provide auxiliary means for defining the entrance-point to the block without introducing any insulated joints into the rails. I accomplish this by providing a relay having a winding connected in shunt to a short length of rail near the transformer at the entrance to the block, and arranged to control the signal jointly with the other track relays in such manner as to render ineffective to control the signal that relay of the pair of relays of the block which responds to the current from the source at the entrance of the block.

My invention will best be understood by reference to the accompanying drawings, in which Figure 1 shows diagrammatically a block slgnal system arranged in accordance with my invention; and Fig. 2 shows my invention applied to a differently arranged signal system of the same general character.

In Fig. 1, A represents the track rails, which may be made conductively continuous for all currents throughout their length. B represents a third-rail, or other supply conductor, and C the generator of the power-current, which has one terminal con-- nected to the third-rail B, and the other to the traclcrails A through the differential choke-coil c. The power-generator C may deliver either direct or alternating current. D D represent alternating-current generators for supplying the signal current. The currents delivered by these generators dif fer from each other in frequency, and, if the power-current is alternating, they differ in frequency from that current. (Z, (7, and (Z represent transmission wires supplied with current from the generators D and D A three-wire transmission system is shown with the wire (Z serving as common return for both frequencies. E and E represent transformers having their primaries supplied with current from the generators D and 1)", respectively, through the line-wires, and the secondaries connected across the track-rails at a distance apart, which, in the drawing, corresponds to the length of a block. Impedances 0 may be inserted in series with the transformer secondaries to prevent saturation of the secondaries by the power-current and to limit the short-circuit current with a train stand-- ing on the track at the transformer. F represents a transformer having its primary connected across the rails between the sup- H and H i t a pair or" relays, which are shown as or t is well-known two-phase induction type, each coinpris .ig a short-circuited sec ondary ueinber 7i carrying the relay contacts and two cooperating windings for pro d ucing the torque in the secondary member. The windings 7L1 of the two relays are both connected to the secondary of the transformer ll, and are consequently supplied with current from the track between the two transformers E and E The other re lay windiu it are connected to different line-wires lvough step-down transformers al and 5 respectively, so that they are supplied wits currents of different frequency.

1 is, aliough the windings A of both reranslorniers E and E L norn'ially traversed by current supto the track by both transformers E E the relay H responds only to curfrom transformer E and, the relay ll col 1 to current from transformer 11 Any suitable means, such condensers may 3e employed for producing a proper phase elatiin between the currents of windings 7i and ii? of each relay. ll represents a sig- "ding the portion of track oetween the tiansio "rue E and E the direction of traliic icing as indicated by the arrow, ll represents a third relay, which may also be of the two-phase induction type. This relay has two tract: windings, Z which are connected in s: ant to short lengths of rail opposite ach other and adjacent to tr: ns ifoi'nier E whil the winding Z sup ilieil indepcndently o" the track circuit with ourrt. the saunifreouency as that delivered by i or ll? The voltage impressed on .1 is that due to the voltage drop in the rail lengths shunted by them, which voltage, becaus: of the skin effect produced by the alternating signal. current is much hip than would be produced by di rect current of the some amount. As long as a bloch' clear, both relays H and H are energized. as shown, their front contacts completing the circuit for the operating niecl'ianisnr of signal K, so that signal 1*:

stands at clear. llelay L is normally deenergized, since the normal current that lions from the secindary of transformer through the track to the right of the trans former, is insuflicient in amount to produce enough c irent i in the track windings Z" to give the relay enough torque to hold its contacts closed,

ow, if a train is amproaching the block, that is approaching transformer from the it, it draws an increasing current from t trns'foruier, and at tile same time rec, "oltage supplied to the track by t .oriner. Relay H which responds on rent fl oin transifo 'mer li is not a I has its torque gradua uce l, as the train comes near the meteor block, and when the train is a certain distance away from transformer E relay l-l" will open its contacts. This would put signal K atdanger, if it were not for the relay L. Before relay H opens its contact, the increased current drawn from transformer E by the approaching train increases the drop of potential in the ails immediately to the right of this transformer, so as to increase the current in the track winding Z of the relay L. This increase is sullicient to cause relay L to close its contacts, and. its upper front contacts short-circuit the t'ain passes over the short lengths of "ail spanned )y the track windings l of relay L. When the train reaches trans former E relay L is wholly deenergized and drops its contacts, thereby causing signal K to go to danger. The circuit of the winding Z of relay L passes tl'irough contacts 0 on the signal, so ar nged that when the signal has gone to danger, the circuit of this winding is opened. The purpose of this arrangement is to avoid the possibility, when a train has passed transfm'uier i l some distance, but has not reached trans former F, so that relay ll? i still energized, of a second train approaching transformer i and drawing sullicient current from the lrans'lbrmer to energize relay windings Z, thereby causing relay L to shun the contact .o:f rela H and clear the signal. Since the winding Z runs through conta L on the signal its circuit is open when the signal. at danger, relay L can only serve to prercnt the signal from being thrown to danger by relay H when the signal is at clear; butcannot cause the signal to clear it it is once at danger and relay H is open. The opouing of relay il will always throw the signal K to danger, regardless of the condition oi. relay l1, so that a train approaching the block cannot prevent the signal from being thrown to danger by a train, hacking into the block at the other end.

In addition. to the contacts shunting the contacts of relay H relay ll has a second pair of front contacts connected in iarzllel with back contacts on relay lil This arrangement is not absolutely essential, but has the following advantage. If these contacts were not employed, and it the block were already occupied by a train so tlu a. second train, approaching the block and finding signal K at danger, waited for it to cl air, then when the first train ran out of the block, allowing relay H to close its contacts, the signal. K would not clear, because the second train would be close enough to trans former ll to prevent relay i k from picking up, while the winding Z of relay L would be opened at contacts is, so that relay ll would not pick up its contacts. The second train would thus be unnecessarily delayed. This is not a serious matter, since in automatic block signal systems it is ordinarily the rule for a train, on finding a signal at danger, to wait a certain length of time and then proceed through the block under con trol. The additional contacts, above men tioned, however, avoid unnecessary delay. The first train, as long as it is in the last half of the block, holds relay H deenergized, so that the back contacts of this re ay are closed. These back contacts are in shunt to the contacts on the signal, as well as to the lower front contacts of relay L, so that with relay H decnergized, winding Z of relay L is energized. Therefore, if a train is waiting at the signal for it to clear, relay L will be energized before the train ahead leaves the block. Consequently relay L shunts the front contacts of relay H", so that when relay l l picks up its contacts as the train ahead leaves the block, the circuit of the operating mechanism of signal K is closed, and this signal clears. The opening of the back contacts of relay H. when this relay picks up, does not deenergize relay winding since the lower front contacts or relay L are in shunt to the back contacts of relay H so that when relay L is energized, it remains energized as long as a train is standing near transformer E and to the right of the terminals of windings Z. Thus, by the use of these auxiliary contacts, the signal K is caused to clear as soon as the first train passes out of the block, but would be immediately returned to danger, if the first train should again back into the block.

My invention is not limited to systems in which the adjacent sources of current are of different frequency, or of different character; but is applicable to any system in which the sources of current are connected across the rails at intervals, and pairs of relays are supplied from the track between two adjacent sources, each relay responding only to current from one source. Vhile in Fig. 1, in order to render each relay responsive to current from one source only, the adjacent sources are caused to supply currents of different character, in Fig. 2, each relay is rendered responsive to current from one source only by its connection to the track. This connection is such that normally no current flows through the track winding of the relay, except that from one adjacent source, and any current that does flow through the track winding of the relay from the other adjacent source cannot actuate the relay, because it is of the wrong phase.

In Fig. 2, the adjacent transformers E and F are supplied from the same generator D. In place of the transformer F of Fig. 1, a low impedance f is connected across Kil the rails, and the track winding 71. of relays H and H are connected in shunt to short lengths of rails on opposite sides of the impedance f. This impedance may be connected diagonally across the rails, as shown, so as to cause the track connections of relays 11 and H to overlap, as described in my former application, Serial No. $35,861, filed June 1, 1908. Vv ith this arrangement of the relays, they are more conveniently placed at the middle of the block, instead of near the signal, as in Fig. 1, in which figure the relays are placed near the signal simply to reduce the number of wires to the smallest amount. The relay L, as before, has its contacts connected in shunt to the contacts of relay H so that when the relay L is energized, relay H is rendered ineffective to putthe signal at danger. As before, the relay winding Z has its circuit carried through contacts is on the signal, for reasons above pointed out. The other set of contacts on. relay L shown in Fig. 1 in shunt to back contacts of relay H are omitted in Fig. 2, in order to simplify the wiring. As has been pointed out, the addition of these contacts is not essential. The connection of the track winding l of relay L, is som what different in Fig. 2 from that of Fig. 1. Instead of being connected in shunt to short rail-lengths lying wholly to the rightof transformer FF, they are connected in shunt to short rail-lengths lying equally on opposite sides of the transformer. Thus, normally, there is no current flowing through the windings P, but a train approaching transformer E from the right produces a flow of current through these relay windings because the voltage drop in the rails to the right of the transformer is then greater than that to the left. Either con nection of the relay windings Z may be used with either the system of Fig. 1 or that of Fig. 2, the arrangement of Fig. 1 giving a somewhat greater maximum torque to the relay L, while that of Fig. 2 gives a wider range of torque if the transformer E is of poor regulation, so that the current does not increase very greatly when a train approaches, and furthermore gives the relay a back torque to force it open very positively when the train passes to the left of transformer E I do not desire to limit myself to the particular connections and arrangement of parts here shown, but aim' in the appended claims to cover all modifications which are within the scope of my invention.

Vhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. In a block signal system, in combination with a railway having both rails conductively continuous for all currents, sources of alternating current connected across the rails at intervals, adjacent sources differing in ma utter, a pair of relays supplied with current;- lfroni the muck between two adjacent sliailrc each responding to current from one adjacen source only, a signal near one of said sources controlled by the pair of relays, and a relay hating winding connected in. shunt to a portion of rail near the source adjali'entto the signal, the said porlion ol? rail being olf such length that the relay is nliirnially deenergized but responds to the incr ased current tlow in the rail produced by an approaching train, said relay 1 ein arranged when energized to render inellectire to control the signal that relay of said pair which responds to the current from said source near the signal.

53. l: a block signal system, in COIlllJl11tlion with a railway having both rails con (ll!(fll\'l3 y continuous for all currents, sources of alternating current connected across the rails a l: intervals, adjacent sources diliiering in charzurter, a pair ol relays supplied with current from the track between two adja cent sources, *ach responding to current from one adjacent source only, a signal near one of said SOl'llCOS controlled by the pair of and a relay having alwinding coni in shunt to a portion of rail near the z ut to the signal, of such length id relay is normally deenergizcd but r l Ads to the increased currenlsllow in the rails prodiu'ed by an approaching train, which relay when energized renders incitetire to control the signal that relay of said pair which responds to the current fl ron'l said source near the signal.

l. in a hlorl signal. system, in combinat on with a railway having both rails conlhart'roly l-mztinuous for all. currents, sources .liun' current connected acriss the inter adj; rent sources (littering in character, a pair oil relays sup ilied with rurrenl tron: the track relays between two adjacent sources, each rcsplnuling to current li' in one adjacent source only, a ial near one l-l said sources controlled by the pair oil relays, and a relay having a winding conlion ot' rail near the nerteo in shunt to a per soul-re adjacent to the si nal. o'l such length tlia said relay is normally drenergized but ends to the increased. current-flow in the prl'ulurcd li y an appromrhing train, said 1y harin r i i-out natal-ts connected in 'allel with 'lronr contacts o'li that relay of ill pair which responds to the current liroin l source near the signal.

n a l)ll)tl\' signal system, in ((illlbl'ltllion with a railnav raring both rails roullumjirely ronlinuous 'l rr all currents, sources o'l alternating current connected across the 1'2lllit ruerrals, adjacent; sources diilerine' in thararler. a pair oi relays supplied with current tram the trurllt between two adjacent; sources, each respoiuling to current from one adjacent source only, a, signal near one ol.

Leases i c portion of rail being of such lei t] that the relay is normally l'leiiier rized hut responds to the increased current flow in tlie l duced by an ap 'iroaching t ain.

in a block sign al system, in combination with a railway having both rails c0nducti'rely continuous for all currents, sources of :idternalting current connected across the rails at intervals, adjacent sources dillering -n character, a pair of relays supplied with current. from the track liietwccn two adjacent sources, each responding to current from one adjacent source only, a F

said sources controlled in all prone nal near one of the pair or relays, a relay having; a windin connected in shunt to a portion of rail near the source adjacent to the signal and jointly with said pair oi re'ays controlling said signal, the said porlion of rail being of such length that the relay is nori'iially deiinergized b responds to the increased current flow in the rail produced by an a iirl'niching train, in d contacts controlled by d sie nal controlling a circuit ol? the last-mentioned relay. 7

in a block fgnal tern, in combination with a railway having both rails condijlctirely continuous l0]? all currents, sources of alleriuitingi' current conn cted across the fails at intervals, adjacent sources diil'leringin character, a pair ojli supplied with current from the tr: cl; between we adjacent sources, each responding to current il ron'i one adjacent source only, a signal near one of said sources controlled liy tie pair of relays, a relay ha ring a winding connected in shunt; to a portion of rail. near the source adjacent to the signal and jointly with said pair of rela a's controlling said signal, the said portion of rail being or such length that title relay normally delinerg'ized but responds to the increased current flow in the rail pro duced by an approaching); train, and means controllel said chat for rendering the last-n1cnt 1 ed, relay inoperative.

I. In a blorl; signal system, in combination with a railway having); both rails conduclirely continuous for all currents, sources at alternating current connected aiross the rails at intervals, adjacent sources dithering in character, a p: 1r oi? relays supplied with current 'lroin "he rack liietween two adjacent sour rs, each responding to current jli'roin one :uljacent sour-re e iii, a signal, inar one oli said seurres controlled by the pal i a relay having a wino no l'vninerted in shunt: to a portion ol? rail nea the il acent 3a ir of to the signal and jointly with relays wx-ntrollnu;- said signal 7 l lion o'l rail lazing ol such length that tie lay is normally delincrgixed but resiouds to the increased current flow in the rail pro duced by an approaching train, and contacts controlled by said signal in circuit with a circuit of the last-mentioned relay and arranged to open said circuit when the signal is at danger.

in a block signal system, in combination with a railway having both rails conductively continuous for all currents, sources of alternating current connected across the rails at intervals, adjacent sources citlering in char actor, a pair of relays supplied with current from the track bet-ween two adjacent sources, each responding to current from one adj acent source only, a signal near one of said sources controlled by the pair of relays, a relay having a winding connected in shunt to a portion of rail no: the source adjacent to the signal and jointly with said pair of relays controlling said signal, the said portion of rail being of such length that the relay is normally deenergized but responds to the increased current flow in the rail produced by an approaching train, and cont-acts controlled by said signal in circuit with a winding of said relay and arranged to deenergize said winding when the signal is at danger.

9. In a block signal syste1n,in combination with a railway having both rails conductively continuous for all currents, sources of alternating current connected across the rails at intervals, adjacent sources differing in character, a pair of relays supplied with current from the track etween two adjacent sources, each responding to current from one adjacent source only, a signal near one of said sources controlled by the pair of relays, a relay having a winding connected in shunt to a portion of rail near the source adjacent to the signahthe said portion of rail being of such length that the relay is normally de'c' nergized but responds to the increased current flow in the rail produced by an approaching train, and means controlled by said signal for rendering the lastn'ientioned relay inoperative, that relay of said pair which responds to current from the source not adjacent to the signal having back contacts connected in shunt to the contacts controlled by the signal.

10. In combination, a stretch of railway track, a source of signaling current connected with the rails thereof, a relay supplied with current from the rails, a signal controlled by said relay, a second relay having a winding connected in shunt to a portion of rail adjacent said source the difference of potential between opposite ends of said portion due to the normal flow of current through said portion being of such an amount that the relay is normally decnen gized but that the relay responds to the currcntflow in the rails due to an approaching train, and means controlled by said second relay when energized for rendering the firstmentioned relay ineffective to control said signal.

11. In combination, a stretch of railway track, a source of signaling current connected with the rails thereof, a relay having a winding connected in shunt to a portion of rail extending to the rear from the con nection of said source, said portion of rail being of such length that the relay is normally deenergized but responds to the current-flow due to an approaching train, and a signal controlled by said relay.

12. In a railway signaling system, in combination with the rails of a railway, a source of current connected across the rails, a relay having one winding connected in shunt vith a portion of rail adjacent the source, the portion being of such length that the relay is normally deenergized but re sponds to the current-flow in the said rail due to an approaching train, and a signal controlled by the relay.

13. In combination, a stretch of railway track, a source of current connected across the rails of said stretch, a relay having a winding connected in shunt to a portion of rail adjacent said source, the difference of potential between opposite ends of said portion due to the normal flow of current being such that the relay is normally de'elnergized, but the difference of potential between opposite ends of said portion due to an approaching train being such that the relay is then energized, and a signal controlled by said relay.

In witness whereof, I have hereunto set my hand this 20th day of July, 1908.

LAURENCE A. HAWKINS.

\Vitnesses BENJAMIN B. HULL, HELEN Gnronn.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents, Washington, D. U. 

